/*
 * This file is part of Applied Energistics 2. Copyright (c) 2013 - 2014, AlgorithmX2, All rights reserved. Applied
 * Energistics 2 is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General
 * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any
 * later version. Applied Energistics 2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
 * Public License for more details. You should have received a copy of the GNU Lesser General Public License along with
 * Applied Energistics 2. If not, see <http://www.gnu.org/licenses/lgpl>.
 */

package appeng.client.render;

import java.util.Random;

import net.minecraft.client.Minecraft;
import net.minecraft.client.multiplayer.WorldClient;
import net.minecraft.client.renderer.GLAllocation;
import net.minecraft.client.renderer.OpenGlHelper;
import net.minecraft.client.renderer.RenderHelper;
import net.minecraft.client.renderer.Tessellator;
import net.minecraftforge.client.IRenderHandler;

import org.lwjgl.opengl.GL11;

public class SpatialSkyRender extends IRenderHandler {

    private static final SpatialSkyRender INSTANCE = new SpatialSkyRender();

    private final Random random = new Random();
    private final int dspList;
    private long cycle = 0;

    public SpatialSkyRender() {
        this.dspList = GLAllocation.generateDisplayLists(1);
    }

    public static IRenderHandler getInstance() {
        return INSTANCE;
    }

    @Override
    public void render(final float partialTicks, final WorldClient world, final Minecraft mc) {
        final long now = System.currentTimeMillis();

        if (now - this.cycle > 2000) {
            this.cycle = now;
            GL11.glNewList(this.dspList, GL11.GL_COMPILE);
            this.renderTwinkles();
            GL11.glEndList();
        }

        float fade = now - this.cycle;
        fade /= 1000;
        fade = 0.15f * (1.0f - Math.abs((fade - 1.0f) * (fade - 1.0f)));

        GL11.glDisable(GL11.GL_FOG);
        GL11.glDisable(GL11.GL_ALPHA_TEST);
        GL11.glDisable(GL11.GL_BLEND);
        GL11.glDepthMask(false);
        GL11.glColor4f(0.0f, 0.0f, 0.0f, 1.0f);

        final Tessellator tessellator = Tessellator.instance;

        for (int i = 0; i < 6; ++i) {
            GL11.glPushMatrix();

            switch (i) {
                case 1 -> GL11.glRotatef(90.0F, 1.0F, 0.0F, 0.0F);
                case 2 -> GL11.glRotatef(-90.0F, 1.0F, 0.0F, 0.0F);
                case 3 -> GL11.glRotatef(180.0F, 1.0F, 0.0F, 0.0F);
                case 4 -> GL11.glRotatef(90.0F, 0.0F, 0.0F, 1.0F);
                case 5 -> GL11.glRotatef(-90.0F, 0.0F, 0.0F, 1.0F);
                default -> {}
            }

            tessellator.startDrawingQuads();
            tessellator.setColorOpaque_I(0);
            tessellator.addVertexWithUV(-100.0D, -100.0D, -100.0D, 0.0D, 0.0D);
            tessellator.addVertexWithUV(-100.0D, -100.0D, 100.0D, 0.0D, 16.0D);
            tessellator.addVertexWithUV(100.0D, -100.0D, 100.0D, 16.0D, 16.0D);
            tessellator.addVertexWithUV(100.0D, -100.0D, -100.0D, 16.0D, 0.0D);
            tessellator.draw();

            GL11.glPopMatrix();
        }

        if (fade > 0.0f) {
            GL11.glEnable(GL11.GL_BLEND);
            GL11.glDisable(GL11.GL_TEXTURE_2D);

            OpenGlHelper.glBlendFunc(770, 771, 1, 0);
            RenderHelper.disableStandardItemLighting();

            GL11.glEnable(GL11.GL_TEXTURE_2D);
            GL11.glColor4f(fade, fade, fade, 1.0f);
            GL11.glCallList(this.dspList);

            RenderHelper.enableStandardItemLighting();
        }

        GL11.glEnable(GL11.GL_FOG);
        GL11.glEnable(GL11.GL_ALPHA_TEST);
        GL11.glEnable(GL11.GL_BLEND);
        GL11.glDepthMask(true);

        GL11.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
    }

    private void renderTwinkles() {
        final Tessellator tessellator = Tessellator.instance;
        tessellator.startDrawingQuads();

        for (int i = 0; i < 50; ++i) {
            double iX = this.random.nextFloat() * 2.0F - 1.0F;
            double iY = this.random.nextFloat() * 2.0F - 1.0F;
            double iZ = this.random.nextFloat() * 2.0F - 1.0F;
            final double d3 = 0.05F + this.random.nextFloat() * 0.1F;
            double dist = iX * iX + iY * iY + iZ * iZ;

            if (dist < 1.0D && dist > 0.01D) {
                dist = 1.0D / Math.sqrt(dist);
                iX *= dist;
                iY *= dist;
                iZ *= dist;

                final double x = iX * 100.0D;
                final double y = iY * 100.0D;
                final double z = iZ * 100.0D;
                final double d8 = Math.atan2(iX, iZ);
                final double d9 = Math.sin(d8);
                final double d10 = Math.cos(d8);
                final double d11 = Math.atan2(Math.sqrt(iX * iX + iZ * iZ), iY);
                final double d12 = Math.sin(d11);
                final double d13 = Math.cos(d11);
                final double d14 = this.random.nextDouble() * Math.PI * 2.0D;
                final double d15 = Math.sin(d14);
                final double d16 = Math.cos(d14);

                for (int j = 0; j < 4; ++j) {
                    final double d17 = 0.0D;
                    final double d18 = ((j & 2) - 1) * d3;
                    final double d19 = ((j + 1 & 2) - 1) * d3;
                    final double d20 = d18 * d16 - d19 * d15;
                    final double d21 = d19 * d16 + d18 * d15;
                    final double d22 = d20 * d12 + d17 * d13;
                    final double d23 = d17 * d12 - d20 * d13;
                    final double d24 = d23 * d9 - d21 * d10;
                    final double d25 = d21 * d9 + d23 * d10;

                    tessellator.addVertex(x + d24, y + d22, z + d25);
                }
            }
        }

        tessellator.draw();
    }
}
